Method of electropolishing uranium



United States Patent M METHOD OF EDECTROPOLISI-HNG URANIUM David E.Walker, Chicago Heights, and Robert A. Noland, Chicago, 11]., assignorsto the United States of America as represented by the United StatesAtomic Energy Commission No Drawing. Application July 18, 1949 SerialNo. 105,456

4 Claims. (Cl. 204-15) This invention deals with an electrolyte and amethod of polishing the surfaces of uranium articles, and in particularwith a method of electropolishing such surfaces.

For many uses of uranium articles and metal, the surfaces should besmooth. If metallographic studies are to be made on uranium surfaces,for instance, a smooth and homogeneous condition is desirable. Polishingof uranium metal by mechanical means was found to be unsatisfactory,because the uranium encountered plastic deformation so that themetallographic examination did not give a true picture of the originalgrain structure.

It is an object of this invention to provide a method of polishinguranium surfaces in which no plastic deformation of the uranium takesplace.

It is another object of this invention to provide a method of polishinguranium surfaces by which an evenly smooth and bright surface isobtained.

It is another object of this invention to provide an electrolyte forelectropolishing.

It is another object of this invention to provide a method of polishinguranium surfaces by which the corrosion resistance of the uranium isincreased and by which the bright surface obtained is distinguished by arelatively long service life even when in contact with air.

It is another object of this invention to provide a method of polishinguranium surfaces so that the uranium metal may be stored after polishingand prior to coating or plating without thereby impairing the adherenceof such coatings.

It is still another object of this invention to provide a process forpreparing uranium for coatings by which the adherence or bond of saidcoatings is greatly improved.

According to this invention, an electrolyte has been found particularlysuccessful which contains sulfuric acid, glycerine, and Water preferablyin concentrations ranging from 35 to 65% by volume of sulfuric acid(96%), from 1 to 20% by volume of glycerine, and from 25 to 55 by volumeof water. The best results were obtained with concentrations of 38 to55% sulfuric acid, to 14% of glycerine, and 33 to 50% of water, whichcorrespond to mixtures of three to five parts by volume of sulfuricacid, one part by volume of glycerine, and three to four parts by volumeof-water. The electrolyte of this invention is especially useful forelectropolishing uramum.

The process of this invention is carried out by immersing the uraniumarticle into the electrolyte, making the article the anode in anelectric circuit and passing electric current, preferably with a voltageof from 10 to 15 volts, through the circuit. It is advantageous, thoughoptional, to discontinue the electrolysis by intermittently withdrawingthe anode from the electrolyte whereby any polarized film formed isremoved and an especially bright surface is obtained.

Uranium articles treated by the process described not only have anessentially improved surface condition but. also a decreasedreactibility with the atmosphere, and,

2,894,883: Patented July 14, 1959 consequently, the polished surfacecondition lasts for an especially long time. It has been found thatarticles treated by the process of this invention stay bright for atleast four to eight hours, but, in some cases, even for two weeks.

In the following example, the preferred embodiment of the process ofthis invention is illustrated without the intention to have the scope ofthe invention limited to the details given therein.

Example A uranium article to be polished was immersed in an electrolytecontaining five parts by volume of sulfuric acid, one part by volume ofglycerine, and three parts by volume of water. This uranium article wasanodically connected in a circuit which included a cathode arrangedthree inches from said anode. By using a potential of from 10 to 15volts, a current was passed through this electric circuit. The anode wasalternately withdrawn from the bath and reimmersed at time intervals offrom three to five seconds.

The article, thus polished, showed an extremely bright and smoothsurface which remained in this condition after eight hours of contactwith the atmosphere.

While a preferred embodiment of the present invention has been describedabove, modifications may be made without departing from the spirit ofthe invention. Thus, this invention is to be limited only by the scopeof the appended claims.

What is claimed is:

1. The method of electropolishing a uranium article, comprisingassembling an electrical circuit including said article as the anode, acathode, and an electrolyte containing from 35 to by volume of sulfuricacid, from 1 to 20% by volume of glycerine, and from 25 to 55% by volumeof water, and passing an electrical current through said circuit topolish the surface of said uranium article.

2. The method of electropolishing a uranium article, comprisingassembling an electrical circuit including said article as the anode, acathode, and an electrolyte containing from 38 to 5 5% by volume ofsulfuric acid, from 10 to 14% by volume of glycerine, and from 33 to 50%by volume of water, and passing an electrical current through saidcircuit to polish the surface of said uranium article.

3. The method of electropolishing a uranium article, comprisingassembling an electrical circuit including said article as the anode, acathode, and an electrolyte at room temperature and containing from 35to 65% by volume of sulfuric acid, from 1 to 20% by volume of glycerine,and from 25 to 55% of water, and passing an electrical current of from10 to 15 volts through said circuit to polish the surface of saiduranium article.

4. A method of electropolishing a uranium article, comprising assemblingan electrical circuit including said article as the anode, a cathodeabout three inches away from said anode, and an electrolyte at roomtemperature containing about five parts by volume of sulfuric acid, onepart by volume of glycerine, and three parts by volume of water, passingan electric current of 10 to 15 volts through said circuit, andalternately withdrawing and reirnmersing said anode from saidelectrolyte at time intervals of from three to five seconds.

References Cited in the file of this patent UNITED STATES PATENTS1,462,421 Pearson et al. July 17, 1923 1,787,672 Davenport Jan. 6, 19312,315,695 Faust Apr, 6, 1943 FOREIGN PATENTS 500,009 Great Britain Feb.1, 1939

1. THE METHOD OF ELECTROPOLISHING A URANIUM ARTICLE, COMPRISINGASSEMBLING AN ELECTRICAL CIRCUIT INCLUDING SAID ARTICLE AS THE ANODE, ACATHODE, AND AN ELECTROLYTE SAID TAINING FROM 35 TO 65% BY VOLUME OFSULFURIC ACID, FROM 1 TO 20% BY VOLUME OF GLYCERINE, AND FROM 25 TO 55%BY VOLUME OF WATER, AND PASSING AN ELECTRICAL CURRENT THROUGH SAIDCIRCUIT TO POLISH THE SURFACE OF SAID URANIUM ARTICLE.